I didn't do farrier work myself but owned horses and have watched the farriers do their job countless times, in addition to having taken a course on how to do it. Based on that knowledge, I'd say you should be sharpening it OFTEN. You're cutting silica-embedded fibrous material with a push cut, and the steels used in those knives are typically not the most carbide-rich, so you're going to RAPIDLY experience edge wear. I'd be touching it up at every opportunity you have, really. A little work done very frequently will keep it performing its best vs. allowing it to degrade too far and then needing to do serious repair of the geometry, which is much more of a chore on blades with complex shapes like hoof knives.